A human PER.C6 cell line, exemplified by cells deposited at the ECACC under No. 96022940, derived from retina cells by immortalization with the adenovirus (Ad5) E1a and E1b genes is disclosed in U.S. Pat. No. 5,994,128. Besides the ability to function as packaging cells for E1-deleted adenoviral vectors (U.S. Pat. No. 5,994,128; WO 01/005945), and for producing other viruses (WO 01/38362), E1-immortalized cells, such as PER.C6 cells, can be used to produce recombinant proteins, such as antibodies (WO 00/63403).
Xie et al. (2002) have disclosed a process for serum-free suspension cultivation of E1-immortalized cells. However, the product yields obtained using the culturing processes disclosed in the art for E1-immortalized cells, can be improved.